Ruth Guttman1 & Nitzan Goldschmidt1
The "Sibling Inventory of Differential Experience" (SIDE) aims to assess nonshared experiences in the same family. Siblings are asked to rate their relations to each other in a relative way ("I am more--or less--......than my sib"). Jerusalem MZ and DZ twin pairs (aged 9 to 14) were administered a shortened version of the SIDE, with questions limited to 'sibling closeness', 'sibling antagonism', sibling care taking', and 'sibling jealousy'. Each child was interviewed in three successive years in a cross-sequential design. Average absolute (unsigned) differences in replies were calculated for the MZ and DZ groups. MZ's were found to be more similar than DZ's on each of the scales, indicating genetic influence. Absolute differences between the two groups of twins decreased from year 1 to year 3, i.e.similarities in perception of experiences in the family increased over time in both kinds of twins, but at different levels.
Address: Department of Psychology, Hebrew University,91905 Jerusalem, Israel, Tel. 972-2-6751589, Fax. 972-2-6413313, e-mail msruthg@mscc.huji.ac.il
1Scheinfeld Center for Human Genetics in the Social Sciences, Department of Psychology, The Hebrew University of Jerusalem